I did an engine oil change on my '91 4.0L YJ today with the help of my daughter. Here's how we did it.

Start by getting 6 quarts of oil. I change mine often, so I just use the Wal-Mart store brand 10W-30 motor oil. It comes in 5 quart jugs & 1 quart bottles. I also use Marvel Mystery Oil (MMO) as it seems to help my sticky lifter situation, and it makes up for the larger capacity oil filter I use.

The factory specified oil filter for my '91 4.0L is the Mopar MO 090 oil filter. I use the Motorcraft FL-1A oil filter because it has the same 3/4 X 16 thread pitch mounting plate, the same diameter seal, but more filter area and a larger capacity.

Basic hand tools are all that are required.

I always start with a warm engine. I had driven the Jeep around town today prior to the oil change.

Remove the oil filter first. This will allow the oil from the filter to drain back into the pan, much like removing your finger from the tip of a straw filled with soda. Also you should inspect the sealing surface to insure that the sealing ring from the old filter isn't stuck on the block.

Now drain the oil from the pan. In this case, a 9/16" socket was all that I needed.

Do not reinstall the drain plug until the oil stops draining in a steady stream. Once the stream turns into a drip, you're okay to reinstall the plug.

I usually pre-fill the oil filter about 2/3 of the way with fresh oil. This reduces the time that it takes to build oil pressure.

Be sure to lube the sealing ring of the new filter with fresh oil prior to installation.

Install the new filter. I only hand tighten the filter about 3/4 to 1 complete turn from the time the seal makes contact with the engine block. Realistically, you want it really snug (by hand!) but "Gorilla tight" is uncalled for.

Refill the engine with fresh oil. Prior to starting, make sure that you have adequate oil on the dipstick and there is no fresh oil dripping from the drain plug or in a huge puddle under the Jeep.

Now restart the engine & make sure that your engine builds oil pressure. Once you build oil pressure, leave the Jeep running in Neutral or Park (with the parking brake on!) and look for any sign of an oil leak while running.

While you're under the hood, check out some key items while waiting on the oil to drain. Look at the battery, it should be fairly clean, dry, and the terminals should be free of corrosion.

Check the level & condition of the power steering fluid. Only use power steering fluid or ATF in the power steering reservoir. If it looks dirty or smells "burnt" then you should consider changing it.
NEVER PUT BRAKE FLUID IN THE POWER STEERING!

Check the clutch fluid level & condition in the reservoir. Again, dirty fluid should be a candidate for a fluid change. Use only DOT 3 or 4 fluid from a new sealed container.
NEVER PUT POWER STEERING FLUID OR ATF IN THE CLUTCH FLUID RESERVOIR!

Check the brake fluid level & condition in the reservoir. Again, dirty fluid should be a candidate for a fluid change. Use only DOT 3 or 4 fluid from a new sealed container.
NEVER PUT POWER STEERING FLUID OR ATF IN THE BRAKE FLUID RESERVOIR!

Don't forget the coolant overflow container from the radiator. Refill it with a 50/50 mix of anti-freeze & water. Also check the windshield washer fluid level.

Max, thanks for taking the time to do this write up ! Sometimes, the simplist things are the ones that get us hahah! Good to have this on hand!

BTW, not to hijack the thread, did you install the Transgo kit for your buddy who had the late shifting auto?

Cameron

__________________
"All that we are is the result of what we have thought. If a man speaks or acts with an evil thought, pain follows him. If a man speaks or acts with a pure thought, happiness follows him, like a shadow that never leaves him."
- Buddha

Max, thanks for taking the time to do this write up ! Sometimes, the simplist things are the ones that get us hahah! Good to have this on hand!I see folks on here who have had no exposure to even the simplest tasks and ask what most wrench spinners would call a "stupid question" or worse they won't ask because they don't want to appear inept. The truth is that these folks are probably plenty smart in their own field of expertise, but want to learn about their Jeep. Hopefully, this will help some questions for the "new" guys & gals.

BTW, not to hijack the thread, did you install the Transgo kit for your buddy who had the late shifting auto?No I haven't. I suggested it to him and he wants to do it, but I just found out that he has no working speedometer and a CEL on. I want to find out what the deal is there first, and then go on to the Transgo kit. Where did you purchase your Transgo kit? I've had a bit of difficulty locating one for a TF904.

"I see folks on here who have had no exposure to even the simplest tasks and ask what most wrench spinners would call a "stupid question" or worse they won't ask because they don't want to appear inept. The truth is that these folks are probably plenty smart in their own field of expertise, but want to learn about their Jeep. Hopefully, this will help some questions for the "new" guys & gals."

hahha...thats me! I should really start doing my own oil change (now I have a house and garage it should be easier) but, I do it mostly to help my mechanic out.

"Where did you purchase your Transgo kit? I've had a bit of difficulty locating one for a TF904."

It's funny you ask this as I am having trouble as well! Did you try Summit Racing? Also, I found Transgo's website, but I didn't see anything mentioned about a TF904. Also, I am sure my is a TF904 but how would I Know for sure?

__________________
"All that we are is the result of what we have thought. If a man speaks or acts with an evil thought, pain follows him. If a man speaks or acts with a pure thought, happiness follows him, like a shadow that never leaves him."
- Buddha

__________________
"All that we are is the result of what we have thought. If a man speaks or acts with an evil thought, pain follows him. If a man speaks or acts with a pure thought, happiness follows him, like a shadow that never leaves him."
- Buddha

Anyway I want to question the use of Marvel Mystery Oil in your oil when changing the oil. Unless you add it before the oil change and run the motor for a while. It seems to me that the Marvel Mystery Oil just thins the fresh oil??

Very cute kid, she made me smile through the whole thread, thanks.Thanks! She sure is a joy to have around!

Anyway I want to question the use of Marvel Mystery Oil in your oil when changing the oil. Unless you add it before the oil change and run the motor for a while. It seems to me that the Marvel Mystery Oil just thins the fresh oil??I use it in the fresh oil of every oil change. It seems to have quieted down my lifter tick considerably over the course of the last year. I use a 1/2 quart to a quart (depending on how much extra I need to top up the oil from using the higher capacity filter) and I leave it in for the duration of the oil's service life. I'm pleased with the results so far, so I guess that's all the proof I need.